The present invention relates to a lip seal device having a lip seal in sliding contact with a rotary shaft.
A lip seal device comprising a case surrounding a rotatably supported rotary shaft and a lip seal whose inner circumferential portion is curved toward a sealed fluid and is in sliding contact with the outside circumferential surface of the rotary shaft has been well known. A similar lip seal device having a lip seal whose sealing surface on a rotary shaft is provided with a spiral groove is disclosed in the U.S. Pat. Nos. 3,857,156 and 3,929,341. The sealing performance of the latter lip sealing device having a spiral groove is better during the rotation of the rotary shaft than that of the former lip seal device not having such a spiral groove. On the other hand, the sealing performance of the latter lip seal device having a spiral groove is much worse during the stoppage of the rotation of the rotary shaft than that of the former lip seal device not having a spiral groove.
Another lip seal device having a lip seal whose sealing surface on the rotary shaft include one or two annular grooves is disclosed in Kokai 55-30542. However, Kokai 55-30542 does not teach a contact force differential between the sealing surfaces on opposing sides of the annular groove. Accordingly, the sealing surface furthest from the pressurized fluid is not properly lubricated resulting in premature wearing of the sealing surface thereof.